Micro electrochemical energy storage cells

ABSTRACT

Thin-film micro-electrochemical energy storage cells (MEESC) such as microbatteries and double-layer capacitors (DLC) are provided. The MEESC comprises two thin layer electrodes, an intermediate thin layer of a solid electrolyte and optionally, a fourth thin current collector layer; said layers being deposited in sequence on a surface of a substrate. The MEESC is characterized in that the substrate is provided with a plurality of through cavities of arbitrary shape, with high aspect ratio. By using the substrate volume, an increase in the total electrode area per volume is accomplished.

NOTICE OF MULTIPLE REISSUE APPLICATIONS

More than one reissue application has been filed with respect to thepresent Pat. No. 6,197,450, the first being application Ser. No.10/382,466, filed Mar. 6, 2003, and the second, which is a continuationof the first, being application Ser. No. 11/866,722, filed Oct. 3, 2007.

FIELD OF THE INVENTION

This invention relates to thin film micro-electrochemical energy storagecells (MEESC), such as microbatteries and double-layer capacitors (DLC).

BACKGROUND OF THE INVENTION

Advances in electronics have given us pocket calculators, digitalwatches, heart pacemakers, computers for industry, commerce andscientific research, automatically controlled production processes and ahost of other applications.

These have become possible largely because we have learned how to buildcomplete circuits, containing millions of electronic devices, on a tinywafer of silicon no larger than 25-40 mm square and 0.4-0.5 mm thick.Microelectronics is concerned with these miniaturized integratedcircuits (ICs), or “chips” as they are called. In a circuit, electricalenergy is supplied from, for example, a microbattery or a double-layercapacitor (DLC) and is changed into other forms of energy by appliancesin the circuit, which have resistance.

Recently, with the tendency of miniaturizing of small-sized electronicdevices, there have been developed thin-film microbatteries, which haveseveral advantages over conventional batteries, since battery cellcomponents can be prepared as thin (1-20 μm) sheets built up as layers.Usually, such thin layers of the cathode, electrolyte and anode aredeposited using direct-current and radiofrequency magnetron sputteringor thermal evaporation.

The area and thickness of the sheets determine battery capacity andthere is a need to increase the total electrode area in a given volume.Thin films result in higher current densities and cell efficienciesbecause the transport of ions is easier and faster through thin-filmlayers than through thick layers.

U.S. Pat. Nos. 5,338,625 and 5,567,210 describe thin-film lithium cells,especially thin-film microbatteries having application as backup orprimary integrated power sources for electronic devices and method formaking such. The batteries described in these references are assembledfrom solid state materials, and can be fabricated directly onto asemiconductor chip, the chip package or the chip carrier. Thesebatteries have low energy and power. They have an open circuit voltageat full charge of 3.7-4.5 V and can deliver currents of up to 100μA/cm². The capacity of a 1 square cm microbattery is about 130 μA/hr.These low values make these batteries useful only for very low powerrequirements in some microelectronic circuits.

A double-layer capacitor (DLC), as opposed to a classic capacitor, ismade of an ion conductive layer between two electrodes. In order to makean electric double-layer capacitor smaller and lighter without anychange in its capacitance, it is necessary to increase the energy. Thismay be accomplished, for example, as described in U.S. Pat. No.5,754,393, by increasing the working voltage by use of an electrolytehaving a high decomposition voltage.

Advanced etching technologies, such as reactive-ion etching (RIE),electron-cyclotron-resonance (ECR) etching and inductively coupledplasma (ICP) etching have been developed to etch semiconductor deviceshaving extremely small features sizes. By using the ICP technique it ispossible to etch small diameter through-cavities such as through-holeswith a very high aspect ratio and smooth surfaces in a substrate such asa silicon wafer.

The present invention is based on a novel approach, according to which athin-film micro-electrochemical energy storage cell (MEESC) such as aDLC or a microbattery is created on a macroporous substrate, thuspresenting increased capacity and performance. By using the substratevolume, an increase in the total electrode area per volume isaccomplished. The cavities within a substrate are formed by deep wet ordry etching of the substrate. For example, holes may be formed by anInductive Coupling Plasma (ICP) etching using the Bosch processdescribed in U.S. Pat. No. 5,501,893.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide amicro-electrochemical energy storage cell (MEESC) such as a DLC or amicrobattery exhibiting superior performance as compared to such cellsknown in the art. A more particular object of the invention is toprovide a DLC or a microbattery with up to two orders of magnitudeincrease in capacity.

The above objects are achieved by the present invention, wherein athin-film MEESC is formed on a substrate having etched structures. Theuse of such a substrate increases the available area for thin filmdeposition, thus leading to an increase in volume, i.e. capacity of thecell.

Thus, the present invention provides a thin-film micro-electrochemicalenergy storage cell (MEESC) comprising two thin layer electrodes andintermediate to these electrodes, a thin layer of a solid electrolyteconsisting of an ionically conducting or electronically non-conductingmaterial such as glass, polymer electrolyte or polycrystalline material,and optionally a fourth thin current collector layer, all these layersbeing deposited in sequence on a surface of a substrate, wherein theMEESC is characterized in that the substrate is provided with aplurality of cavities with high aspect ratio; said electrodes, solidelectrolyte and current collector layers being deposited also throughoutthe inner surface of said cavities and on both surfaces.

In a preferred embodiment the MEESC of the present invention is a thinfilm microbattery which comprises:

a thin layer anode consisting of alkali metal (M), alkali metal alloy,for example alkali metal alloy based on Zn, Al, Mg, or Sn or in thecharged state consisting of lithiated carbon or graphite,

a thin layer cathode consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, TiS₂, V₂O₅,V₃O₈ or lithiated forms of the vanadium oxides,

a solid electrolyte intermediate to the anode and cathode layers, whichconsists of a thin layer of an ionically conducting or electronicallynon-conducting material such as glass, polymer electrolyte orpolycrystalline material, and

optionally, a current collector layer; the anode or cathode layer beingdeposited on a surface of a substrate, the microbattery beingcharacterized in that the substrate is provided with a plurality ofcavities with high aspect ratio; said anode, cathode and solidelectrolyte layers being deposited also throughout the inner surface ofsaid holes.

In cases wherein the microbattery is a lithium ion type, such a batteryis fabricated in the discharge state where the cathode is fullylithiated and the alloy, the carbon or the graphite anode is not chargedwith lithium.

According to another preferred embodiment, the MEESC of the presentinvention is a double-layer capacitor (DLC), which comprises twoelectrodes made of high surface area carbon powder and intermediate tothese electrodes a solid electrolyte layer, preferably a polymerelectrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 is a schematic diagram of a thin-film microbattery coating asilicon wafer with through-holes.

FIG. 2 is a schematic view of a test cell.

DETAILED DESCRIPTION OF THE INVENTION

Thin-film rechargeable power sources can be applied for computer memoryback-up and many other uses, such as autonomous micro electro-mechanicalsystems (MEMS). Lithium batteries have been brought recently to anextreme stage of miniaturization. Sequential gas phase depositiontechniques of anode, electrolyte and cathode layers make it possible toincorporate such lithium batteries on a silicon substrate. In a chemicalvapor deposition process gases and/or vapors react to form a solidcompound. This reaction usually takes place after adsorption and partialdecomposition of the precursors on the substrate surface, thoughreaction in the gas phase is possible.

The thin-film MEESC of the present invention consists of a sandwich ofmultiple layers, coating the inside of a through-cavity of arbitraryshape, formed in a substrate, for example by means of Inductive CoupledPlasma (ICP) etching when the substrate is made of silicon. Generally,the substrate material is made of a single crystal or amorphous materialand is selected from glass, alumina, semiconductor materials for use inmicroelectronics, or ceramic materials. The substrate material ispreferably silicon.

The through-cavities etched have very high aspect ratio and smoothsurfaces, both features being essential for achieving uniform coatingand an increase in the area available for thin-film deposition. Thethin-film layers of the electrodes and electrolyte are deposited byeither Chemical Vapor Deposition (CVD), casting or plating techniques.In CVD, gases providing the required materials will pass the cavity,undergo a chemical reaction induced by heat, plasma or a combination ofthe two, and deposit the material uniformly on the inside wall andbetween the cavities.

According to the present invention, for microbattery applications thepolymer electrolyte is designed so as to contain at least one materialthat can be reduced to form an insoluble solid electrolyte interphase(SEI) on the anode surface. Aprotic solvents such as ethylene carbonate(EC), diethylcarbonate (DEC), dimethylcarbonate (DMC), ethyl methylcarbonate (EMC), butyl carbonate, propylene carbonate, vinyl carbonate,dialkylsulfites and any mixtures of these, and metal salts such asLiPF₆, LiBF₄, LiAsF₆, LiCF₃, and LiN(CF₃SO₂)₂ are considered to be goodSEI precursors, as well as other salts such as LiI and LiBr. The polymerelectrolyte further contains a polymer, preferably polyethylene oxide,adapted to form a complex with the metal salt and optionally a nanosizeceramic powder to form a composite polymer electrolyte (CPE).

While lithium metal foil is typically used for the negative electrode,the negative electrode is not specifically restricted as long as itcomprises an electrically conductive film that provides alkali metal ina form effective for the electrode reaction. The preferred microbatteryused in the present invention is a lithium ion type battery fabricatedin the discharge state wherein the anode is made of Al, Sn, Zn, Mg basedalloys, carbon or graphite. Lithium-ion cells made according to thepresent invention are air stable in the discharged state and are chargedonly after the assembly of the cell, thus being more favorable in termsof ease of production.

Similarly, the active substance of the positive electrode is notspecifically restricted as long as it is of a type in which the metalions, e.g. lithium ions are intercalated or inserted during dischargeand taken out during charge of the battery. Inorganic compounds aretypically employed, for example LiCoO₂, LiNiO₂, LiMn₂O₄, and lithiatedvandium oxides for the lithium ion microbattery, while FeS₂ and TiS₂ canbe used for the lithium metal anode microbattery. Fine powders of thesecompounds are cast together with the polymer electrolyte. In addition,it was found that where a composite polymer electrolyte and/or a cathodecontain up to 15% (V/V) of inorganic nanosize powder such as Al₂O₃,SiO₂, MgO, TiO₂ or mixtures thereof, the cell demonstrates improvedcharge-discharge performance.

For the DLC application additional salts can be used such as amonium andalkyl amonium salts. The DLC is made in a similar way as themicrobattery: the electrodes are made in a same manner as the cathodelayer in microbatteries, but the cathode powder is replaced by a highsurface area (over 50 m²/g) carbon.

FIG. 1 shows a possible cylindrical geometry implemented in a substrate,for example silicon, of a microbattery. The anode is made, in thecharged state, of an alkali metal (M), alkali metal alloy or lithiatedcarbon. The preferred alkali metal is lithium and the preferred alloysare Al, Mg, Sn and Zn based alloys. The solid electrolyte is made of anionically conducting glass, preferably Li_(X)PO_(Y)N_(Z) where 2<x<3,2y=3z and 0.18<z<0.43, or Li₂S-SiS₂ glasses doped with up to 5% LiSO₄ or30% LiI, or a poly(ethylene oxide) based polymer electrolyte, preferablycross-linked poly (ethylene oxide) with CF₃SO₃Li or LiN(CF₃SO₂)₂. Thecathode is made of LiCoO₂, LiNiO₂, LiMn₂O₄, TiS₂, V₂O₅, V₃O₁₃ or thelithiated form of these vanadium oxides. The layers are deposited byCVD, plating, casting or similar known coating techniques, preferably byCVD. Contacts to the anode and cathode are made on either the same sideof the wafer using masking, etching, and contact metal deposition, orusing both sides of the wafer.

By etching the substrate with macroporous cavities of various shapes,the microbattery of the present invention has an increased areaavailable for thin film deposition by up to 100 fold. Since the capacityof a battery is directly proportional to its volume, for the samethin-film thickness (typically a few microns for each layer of anode,electrode and cathode and up to a total of about 70 μm), means anincrease in volume of up to about two orders of magnitude, i.e.capacity, to about 10,000 microAmp hour per 1 square cm.

For a circular cavity with diameter d in a wafer of thickness h (“aspectratio”=h/d), the ratio k of surface area after etching to the original,“planar” state is 2 h/d. For a square cavity with side a in the samewafer, k=2 h/a. Thus, for a typical wafer with a thickness of 400 μm(e.g. h=400) and d or a=15 μm, the increase in area is: k=53, while ford=10 μm, k=80.

The invention will be further described in more detail with the aid ofthe following non-limiting examples.

EXAMPLE 1

A microbattery, consisting of a carbon anode, composite polymerelectrolyte and composite LiCoO₂ cathode was fabricated in thedischarged state on a perforated 400 micron thick silicon wafer whichcontains 100 micron in diameter through holes. A thin carbon film wasdeposited by CVD at 850 Celsius by passing a C₂H₄ (10%) Ar (90%) gasmixture for four minutes over the wafer.

A second layer of a composite polymer electrolyte (CPE) was deposited(inside an Ar filled glove box) over the carbon layer by a short vacuumdipping at 50-65 Celsius in acetonitrile (30 ml) suspension consistingof 0.6 g PEO (5×10⁶ MW), 0.05 g EC, 0.1 g LiN(CF₃SO₂)₂ (imide) and 0.03g alumina. After drying, a second layer of CPE was deposited in the sameway to get the desired CPE thickness. A thin cathode layer was deposited(inside the glove box) over the CPE layer by a short vacuum dipping incyclopentanone (10 ml) suspension consisting of 2 g of ball milledLiCoO₂, 0.05 g alumina, 0.2 g PVDF copolymer (ELF 2800) and 0.4 gsub-micron graphite powder. As an option for improving cathodeutilization and power capability, a forth PVDF-graphite layer isdeposited on the cathode.

Poly(ethylene oxide)(P(EO)) was purchased from Aldrich, (averagemolecular weight 5×10⁶) and was vacuum dried at 45° to 50° C. for about24 hours. The imide (Aldrich) was vacuum dried at 200° C. for about 4hours. All subsequent handling of these materials took place under anargon atmosphere in a VAC glove box with an water content<10 ppm. Apolymer electrolyte slurry was prepared by dispersing known quantitiesof P(EO), imide, and ethylene carbonate (EC) in analytical gradeacetonitrile together with the required amount of an inorganic filler,such as Al₂O₃ (Buehler), or SiO₂ with an average diameter of about 150Å.To ensure the formation of a homogeneous suspension, an ultrasonic bathor high-speed homogenizer was used. The suspension was stirred for about24 hours before the composite cathode was cast. The solvent was allowedto evaporate slowly and then the wafers were vacuum dried at 120° C. forat least 5 hours. The electro-chemical characteristics of themicrobattery has been examined in the experimental cell showed in FIG.2, which comprises a hermetically sealed glass container 5, providedwith an outlet 1, connected to a vacuum pump; the glass cover 3 of theglass container is equipped with a Viton O-ring 4. On one side of thewafer a contact was made to the carbon anode and on the other side acontact was made to the cathode. The test cell illustrated in FIG. 2 isconnected by wires 7 to tungsten rods 2 which pass through the cover. Inthe glass container, the battery 6 was cycled between 2.5 and 4.1 V at0.01 mA and at 25° C. using a Maccor series 2000 battery test system.

The cell delivered above 0.4 mAh per cycle for over 20 cycles. TheFaradaic efficiency was close to 100%.

EXAMPLE 2

A DLC, consisting of two carbon electrodes, and composite polymerelectrolyte was fabricated on a perforated 400 micron thick siliconwafer which contains 100 micron in diameter through holes in a similarway as described in Example 1. A thin high surface area carbon powder(500 m²/g) (made by 1000 Celsius pyrolysis of cotton) layer wasdeposited (inside the glove box) on the perforated wafer by a shortvacuum dipping in cyclopentanone (10 ml) suspension consisting of 1 g ofball milled carbon, 0.05 g carbon black and 0.1 g PVDF copolymer (ELF2800). A second layer of a composite polymer electrolyte (CPE) wasdeposited (inside Ar filled glove box) over the carbon layer by a shortvacuum dipping at 50-65 Celsius in an acetonitrile (30 ml) suspensionconsisting of 0.6 g PEO (5×10⁶ MW), 0.05 g EC, 0.1 g LiN(CF₃SO₂)₂(imide) and 0.03 g alumina. After drying, another layer of CPE wasdeposited in the same way to get the desired CPE thickness. A third highsurface area carbon layer was deposited in the same way as the firstone.

By using the procedure described in Example 1 above, the DLC was cycledat 0.01 mA between 1.2 and 2.5 V for over 1000 cycles of 10 secondseach.

EXAMPLE 3

A microbattery, consisting of four thin films: a carbon anode, Al dopedLi₂CO₃ solid electrolyte, LiCoO₂ cathode and carbon current collectorwas fabricated in the discharged state on a perforated 400 micron thicksilicon wafer which contains 60 micron in diameter through holes. A thincarbon film was CVD deposited at 850 Celsius by passing a C₂H₄ (10%) Ar(90%) gas mixture for three minutes over the wafer. A second layer ofthin Al doped Li₂CO₃ solid electrolyte was deposited at 475 Celsius onthe first one by CVD following the procedure described in P. Fragnaul etal. J. Power Sources 54, 362 1995. A third thin layer of LiCoO₂ cathodewas deposited at 500 Celsius on the second one following the proceduredescribed in P. Fragnaul et al. J. Power Sources 54, 362 1995. A fourththin carbon current collector layer was deposited at 800 Celsius on thethird one in the same way as the first one.

This cell was cycled (as described in example 1) at 0.01 mA and at roomtemperature between 2.5 and 4.1 V for more than 10 stable cycles.

1. A thin-film micro-electrochemical energy storage cell (MEESC) in theform of a microbattery, said microbattery comprising: a substrate havingtwo surfaces, a thin layer anode consisting of alkali metal (M), alkalimetal alloy or in the charged state consisting of lithiated carbon orgraphite, a thin layer cathode consisting of LiCoO₂, LiNiO₂, LiMn₂O₄,TiS₂, V₂O₅, V₃O₈ or lithiated forms of the vanadium oxides, a solidelectrolyte intermediate to said anode and cathode layers, consisting ofa tin layer of an ionically conducting or electronically non-conductingmaterial selected from glass, poly(ethylene oxide) based polymerelectrolyte or polycrystalline material, and optionally, a fourthcurrent collector layer; said anode or cathode layer being deposited insequence on both surfaces of said substrate, said microbattery beingcharacterized in that the substrate is provided with a plurality ofthrough cavities of arbitrary shape, with an aspect ratio greater than1, the diameter of said cavities being from about 15μ to about 150μ;said anode, cathode, solid electrolyte layers and optional currentcollector layer being also deposited throughout the inner surface ofsaid cavities.
 2. The microbattery of claim 1, wherein the substrate ismade of a single crystal or amorphous material.
 3. The microbattery ofclaim 2, wherein the substrate material is selected from the groupconsisting of glass, alumina, semiconductor materials for use inmicroelectronics and ceramic materials.
 4. The microbattery of claim 3,wherein the substrate material is made of silicon.
 5. The microbatteryof claim 1, wherein the alkali metal (M) which forms the anode islithium.
 6. A lithium ion type microbattery according to claim 1, beingfabricated in the discharge state where the cathode is fully lithiatedand the alloy, carbon or graphite anode is not charged with lithium. 7.The microbattery of claim 1, wherein the through cavities of thesubstrate are formed by Inductive Coupled Plasma etching.
 8. Themicrobattery of claim 1, wherein the through cavities of the substratehave an aspect ratio of between about 2 to about
 50. 9. The microbatteryof claim 1, wherein said cavities have a cylindrical geometry.
 10. Themicrobattery of claim 1, wherein the solid electrolyte is a polymerelectrolyte based on poly(ethylene oxide) and CF₃SO₃Li, (CF₃SO₂)₂NLi, ormixtures thereof.
 11. The microbattery of claim 1, wherein the solidelectrolyte is selected from Li_(X)PO_(Y)N_(Z) where 2<x<3, 2y=3z and0.18<z<0.43, or LiS-SiS₂ glasses doped with up to 5% LiSO₄ or 30% LiI.12. The microbattery of claim 1, wherein the solid electrolyte is apolymer electrolyte and it comprises between about 2 to about 15% (V/V)high surface area of inorganic, nanosize particles of ceramic powderwhich consists of Al₂O₃, SiO₂, MgO, TiO₂ or mixtures thereof.
 13. Themicrobattery of claim 1, wherein the solid electrolyte comprises Li₂CO₃doped with up to about 10% (% atomic weight relative to Li) of Ca, Mg,Ba, Sr, Al or B.
 14. A self-powered semiconductor component comprising amicrobattery according to claim
 2. 15. A thin-film micro-electrochemicalenergy storage cell (MEESC) in the form of a microbattery, saidmicrobattery comprising: a substrate having two surfaces and including aplurality of through cavities of arbitrary shape, said cavitiescharacterized by having an aspect ratio greater than 1 and extendingbetween said two surfaces; a thin layer anode; a thin layer cathode; andan electrolyte intermediate to said anode and cathode layers; whereinsaid anode layer, said cathode layer, and said electrolyte intermediateto said anode and cathode layers, are deposited over said two surfacesand throughout the inner surface of said cavities.
 16. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said substrate comprisesa single crystal substrate.
 17. A thin-film micro-electrochemical energystorage cell (MEESC) in the form of a microbattery according to claim 16and wherein said single crystal substrate comprises a silicon substrate.18. A thin-film micro-electrochemical energy storage cell (MEESC) in theform of a microbattery according to claim 15 and wherein said substratecomprises a single amorphous material.
 19. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said substrate comprisesat least one material selected from the group consisting of glass,alumina, semiconductors and ceramic materials.
 20. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said anode comprises atleast one material selected from the group consisting of an alkalimetal, an alkali metal alloy, carbon and graphite.
 21. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 20 and wherein said alkali metalcomprises lithium.
 22. A thin-film micro-electrochemical energy storagecell (MEESC) in the form of a microbattery according to claim 20 beingfabricated in the discharge state wherein said cathode layer is fullylithiated.
 23. A thin-film micro-electrochemical energy storage cell(MEESC) in the form of a microbattery according to claim 22 and whereinsaid metal alloy is not charged with lithium.
 24. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 22 and wherein said carbon and saidgraphite are not charged with lithium.
 25. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said cavities have anaspect ratio greater than 1 and up to about
 50. 26. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said electrolytecomprises a polymer electrolyte.
 27. A thin-film micro-electrochemicalenergy storage cell (MEESC) in the form of a microbattery according toclaim 68 and wherein said polymer electrolyte comprises at least onematerial selected from the group consisting of glass, a polyethyleneoxide based polymer, a polycrystalline material, ethylene carbonate(EC), diethylcarbonate (DEC), dimethylcarbonate (DMC), ethyl methylcarbonate (EMC), butyl carbonate, propylene carbonate, vinyl carbonate,dialkylsulfites, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ , LiN(CF ₃ SO ₂)₂ ,LiI and LiBr.
 28. A thin-film micro-electrochemical energy storage cell(MEESC) in the form of a microbattery according to claim 15 and whereinsaid electrolyte is selected from Li _(x) PO _(y) N _(z) where 2<x<3,2y=3z and 0.18<z<0.43, or LiS—SiS ₂ glasses doped with up to 5 % LiSO ₄or 30 % LiI.
 29. A thin-film micro-electrochemical energy storage cell(MEESC) in the form of a microbattery according to claim 15 and whereinthe electrolyte comprises Li ₂ CO ₃ doped with up to about 10 %, ofatomic weight relative to Li, of Al.
 30. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and wherein said anode layercomprises lithium metal foil.
 31. A thin-film micro-electrochemicalenergy storage cell (MEESC) in the form of a microbattery according toclaim 15 and wherein said cathode layer comprises at least one materialselected from the group consisting of LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ ,TiS ₂ , V ₂ O ₅ , V ₃ O ₁₃ , the lithiated form of V ₂ O ₅ and thelithiated form of V ₃ O ₁₃ .
 32. A thin-film micro-electrochemicalenergy storage cell (MEESC) in the form of a microbattery according toclaim 15 and also comprising at least one PVDF-graphite layer depositedon said cathode layer.
 33. A thin-film micro-electrochemical energystorage cell (MEESC) in the form of a microbattery according to claim 15and wherein said anode layer and said cathode layer comprise carbon. 34.A thin-film micro-electrochemical energy storage cell (MEESC) in theform of a microbattery according to claim 33 and wherein saidelectrolyte comprises a polymer electrolyte.
 35. A thin-filmmicro-electrochemical energy storage cell (MEESC) in the form of amicrobattery according to claim 15 and also comprising a currentcollector layer.
 36. A thin-film micro-electrochemical energy storagecell (MEESC) in the form of a microbattery according to claim 35 andwherein said current collector layer is deposited over said anode layer,said electrolyte, and said cathode layer.